Back to EveryPatent.com
United States Patent |
5,061,932
|
Tribe
,   et al.
|
October 29, 1991
|
Road surface sensing system for a vehicle
Abstract
A system for sensing road irregularities from a vehicle modifies an
operational system of the vehicle, such as a suspension system, according
to the type and severity of the sensed irregularity. The system employs a
Doppler Microwave radar sensor arranged to project radiation at a road
surface ahead of the vehicle and includes means for detecting radiation
reflections of which the carrier frequency is amplitude modulated
according to the surface irregularities. An electronic circuit
differentiates the modulated signal to produce a control signal
representative of said surface condition and a controller receives said
signal and modifies the operation of the vehicle system in response
thereto.
Inventors:
|
Tribe; Raglan H. A. H. (Solihull, GB3);
Thomson; Neil G. (Shirley, GB3)
|
Assignee:
|
Lucas Industries Public Limited Company (Birmingham, GB2)
|
Appl. No.:
|
562923 |
Filed:
|
August 6, 1990 |
Foreign Application Priority Data
Current U.S. Class: |
342/70; 73/105; 342/71 |
Intern'l Class: |
G01S 013/60; G01B 005/28 |
Field of Search: |
342/70-72,104
73/105,146
|
References Cited
U.S. Patent Documents
3617993 | Nov., 1971 | Massie et al. | 342/104.
|
3618084 | Nov., 1971 | Balsiger et al. | 342/104.
|
3720818 | Mar., 1973 | Spragg et al. | 73/105.
|
4148027 | Apr., 1979 | Nowogrodzki | 342/104.
|
4354191 | Oct., 1982 | Matsumura et al. | 342/104.
|
4913482 | Apr., 1990 | Hanai et al. | 296/65.
|
Primary Examiner: Barron, Jr.; Gilberto
Attorney, Agent or Firm: Nixon & Vanderhye
Claims
We claim:
1. A road surface sensing system for a vehicle, said system comprising:
a transmitter for projecting electromagnetic radiation having a carrier at
a road surface ahead of a vehicle; and
a receiver for receiving the electromagnetic radiation reflected by the
road surface whereby the carrier of the reflected radiation is amplitude
modulated according to irregularities of the road surface, said receiver
comprising:
detection means for detecting an amplitude modulation signal of the carrier
of the reflected radiation;
differentiating means for differentiating the amplitude modulation signal
from said detection means and for producing a control signal
representative of a road surface condition; and
vehicle system control means, responsive to the control signal from said
differentiating means, for modifying an operating of the vehicle.
2. A system as claimed in claim 1, in which said transmitter is a microwave
transmitter.
3. A system as claimed in claim 1, in which said receiver further comprises
a low pass filter connected between said detection means and said
differentiating means.
4. A system as claimed in claim 1, in which said vehicle system control
means includes comparing means for comparing the control signal at least
one threshold.
5. A system as claimed in claim 4, in which said comparing means includes
discriminating means for discriminating between a positive slope and a
negative slope of the amplitude modulation signal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a system for sensing the irregularities, such as
bumps and pot holes, in a road surface and modifying an operational system
of the vehicle, such as the suspension system, and thereby the running
performance of the vehicle, according to the type and severity of the
sensed irregularity.
2. Discussing of Prior Art
In one known road surface sensing proposal, described in U.S. Pat. No.
4,781,465, the road surface is scanned by directing a light beam onto the
surface at a predetermined distance ahead of the vehicle and monitoring
the distance travelled by the reflected light to produce a signal used for
suspension adjustment. The operation of such a system can be seriously
disturbed by the effect of spurious reflections and the preventive and
corrective expedients necessary to deal with such problems further
increase the manufacturing costs of an already inherently expensive
system.
In another known system, described in U.S. Pat. No. 4,225,950, ultrasonic
sound emissions are directed onto a road surface and reflected signals are
used to influence vehicle performance. The ultrasonic sound signals are,
however, very susceptible to degradation by air turbulence and such
systems are therefore considered to be unreliable.
It has also been proposed to use radar to measure variations in the
distance between the underside of a vehicle and road surface thereunder
and to produce corresponding control signals. However, such a system does
not provide sufficient response time to enable the controlled equipment on
the vehicle to modify the vehicle performance in a satisfactory manner.
SUMMARY OF THE INVENTION
An object of the invention is to provide a road surface sensing system for
a vehicle which is simple and cheap to manufacture and operates more
effectively that some conventional systems.
According to the invention, a road surface sensing system for a vehicle
comprises a transmitter for projecting electromagnetic radiation at a road
surface ahead of a vehicle, a receiver for detecting radiation whose
carrier is amplitude modulated according to irregularities of the surface,
means for differentiating the modulation signal to produce a control
signal representative of the road surface condition, and a vehicle system
controller arranged to receive the control signal and to modify operation
of the vehicle system in response to the control signal.
Preferably the transmitter is arranged to emit microwave radiation.
Preferably the modulated signal is fed to a low pass filter stage to
eliminate system noise prior to differentiation thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example, with reference to
the accompanying drawings in which:
FIG. 1 is a diagrammatic illustration of a vehicle showing part of the
equipment of the system of the invention installed thereon;
FIG. 2 is a diagrammatic side elevation of the vehicle of FIG. 1,
illustrating further details of the system of the invention;
FIG. 3 is a circuit diagram representing the system of the invention;
FIGS. 4a and 4b are graphs representing waveforms arising during operation
of the system, and
FIG. 5a to 5c illustrate various stages in processing the waveform of FIG.
4b to provide the necessary control signals.
DETAILED DISCUSSION OF PREFERRED EMBODIMENTS
Referring to FIGS. 1 and 2, these illustrate a vehicle 1 incorporating a
Doppler microwave sensor 2 disposed substantially centrally of the front
of the vehicle and arranged to direct a radar beam 3 forwardly of the
vehicle to impinge upon the road surface at a predetermined distance from
the front of the vehicle. The single sensor illustrated would be useful to
assess the condition of the road surface generally in front of the
vehicle, but it would be preferable to incorporate one or more alternative
or additional sensors preferably located in alignment with the respective
front wheels of the vehicle so as to assess the road surface condition
under each of these wheels. Such sensors are shown in broken lines at 2'.
The sensors illustrated are of the microwave horn type, but alternative
kinds of sensors, such as planar antennae, may additionally or
alternatively be used.
In FIG. 2, the beam 3 is illustrated encountering a bump 4 in the road
surface, which is shown in an exaggerated form for the purpose of
illustration. A depression or "pot hole 5" is also illustrated and would
be detected by the system of the invention. Return signals collected by
the sensor are fed to an electronic controller 6, which produces output
signals for feeding to one or more system controllers 7 which may be
activated to modify the action of vehicle equipment, such as steering,
suspension or brake management, according to the severity of the
irregularity 4, 5 in the road surface encountered by the vehicle. The
controller 6 may conveniently be an existing on-board "speed over ground"
controller which may already be incorporated in the vehicle for speed
measuring purposes. However, it would be equally possible to incorporate
an individual controller to deal with the surface sensing aspect and
provide appropriate signals to the vehicle system controllers 7. One
example of controlling vehicle performance in response to road surface
condition is to adjust the detection threshold of the vehicle brake
antiskid system to render that system less sensitive when a rough road
surface is encountered. It would also be possible to adjust the stiffness
of the vehicle suspension associated with the side of the vehicle which
will encounter the oncoming rough surface in the form of bumps and/or pot
holes. For example, the suspension may be adjusted so that it will more
readily adsorb the increased road roughness and it will also be possible
to adjust the vehicle ride height in the event that an excessively large
irregularity were encountered. Although it would be possible to use the
system of the invention in conjunction with conventional suspension
systems, the invention may very advantageously be employed in conjunction
with an active suspension system. A further possibility for modifying
vehicle performance is to use the system of the invention to control the
amount of power steering assistance provided, depending upon the nature of
the on-coming road surface.
FIG. 3 illustrates diagrammatically one form of the sensing system of the
invention. The Doppler sensor 2 comprises a microwave generator 20
connected to a power supply 21 for generating a microwave carrier signal
which is emitted as a narrow beam by the horn. A microwave diode 22
located in the horn receives microwaves reflected from the road surface
and from the generator 20, and supplies a detected signal to a
pre-amplifier 10. The carrier signal from the sensor 2 is directed at the
road surface and provides a carrier frequency which, upon impinging on a
bump or pot hole, produces a return signal carrying an amplitude
modulation representative of the bump or pot hole profile. The carrier is
shifted in frequency by the Doppler effect in accordance with the relative
speed between the horn and the ground. The return signal sensed by the
sensor is amplified in a pre amplifier 10 and the amplified signal is fed
into a "speed-over-ground" circuit for various conventional purposes.
FIG. 4a illustrates a typical signal train produced by the sensor 2 in
response to radiation reflected from the sensed road surface and FIG. 4b
illustrates, to an enlarged scale, a typical raw signal representing a
pronounced bump 4 on the road surface. A detector and low pass filter 11
rectifies the signal of FIG. 4b and eliminates or reduces system noise,
leaving a signal carrying the low frequency bump profile characteristic as
illustrated in FIG. 5a, and this signal is thresholded to remove minor
irregularities, the resulting signal being illustrated in FIG. 5b. The
filtered and thresholded signal is then passed to a differentiator circuit
12 where it is differentiated to produce a signal of the kind illustrated
in FIG. 5c. This signal carries the characteristic profile slope of either
a bump or a pot hole. The typical "bump" signal form of FIG. 4 can be seen
to have a rising portion A which is less steep than the falling portion B
of the slope and the differentiated signal obtained (FIG. 5c) can be
compared with reference information to ascertain whether or not the rising
and falling portions of the signal have the correct relationship to
indicate detection of a bump.
The signal form resulting from detection by a pot-hole will be
substantially a mirror image of that in FIG. 4b, with a rising portion A
steeper than the falling portion B, giving rise to a correspondingly
reversed differentiated signal.
The differentiated signal is fed to a comparator stage respectively 13a,
13b assess the signal, by reference, for example, to a pair of threshold
values, to determine whether it represents a bump or a pot hole. These
comparators also act as threshold determining means for assessing the
severity of the sensed road irregularity. The output from the comparator
stage 13 is then fed to a logic stage 14 in which the signals are
processed to produce corresponding outputs for supply to the various
vehicle system controllers 7 which modify the operation of the
corresponding systems so as to obtain the required response in vehicle
behavior.
Although the system illustrated in FIG. 3 is shown as an analog system, it
may be embodied at least partially as a digital system, for instance in a
microprocessor or microcomputer. For instance the functions of the
differentiator 12, the comparator stage 13, the logic stage 14, and at
least part of the detector and filter 11 may be performed in software by a
data processor, which may perform other functions such as speed over
ground measurement and control of brake, steering, and suspension
operation.
Top